Nowadays, MANETs becomes a most types of the networks used in many applications, which support a communications between several sources and destinations without using infrastructure mode. Since these networks are infrastructure free, so it required a mechanism to route the information from the sources to destinations and the routing protocols has been studied deeply. Other consideration that becomes a most important issue is how to connect the MANET to the Internet and the most important parameter is how to interface between these networks. Gateways are most important mechanism to interface between these networks and it must be stable to ensure good quality of services for MANET and Internet connectivity. The main challenges in MANET-Internet connectivity are gateway discovery and gateway selection. Many solutions are proposed and implemented by the different authors/researchers to discover the gateway to the internet so that gateway discovery as we know has been deeply investigated. The second challenge is how to select an optimal gateway and a few different mechanisms have been proposed to select gateways. In this paper we present a review of various gateway selection schemes which are used in MANET to Internet connectivity.